Re: New diagnostic routine - mutex_ownable()

[christos%astron.com@localhost (Christos Zoulas)]

In article <Pine.NEB.4.64.1704300840170.3617%speedy.whooppee.com@localhost>,
Paul Goyette  <paul%whooppee.com@localhost> wrote:
>-=-=-=-=-=-
>
>While working on getting the localcount(9) stuff whipped into shape, I 
>ran across a situation where it is desirable to ensure that the current 
>process/lwp does not already own a mutex.
>
>We cannot use !mutex_owned() since that doesn't return the desired 
>result for a spin mutex, so I'm proposing to add a new routine called 
>mutex_ownable().  This does nothing in normal kernels, but for LOCKDEBUG 
>kernels it does a mutex_enter() followed immediately by mutex_exit(). 
>If the current process already owns the mutex, the system will panic 
>with a "locking against myself" error; otherwise mutex_ownable() just 
>returns 1, enabling its use as
>
> 	KASSERT(mutex_ownable(mtx));
>
>Diffs are attached (including man-page and sets-list updates).
>
>Comments?  Any reason why this cannot be committed?
>
>(Thanks to riastradh@ for the idea and initial review.)

How frequently is this going to be used and what is the performance
penalty for it. I am asking because I am running LOCKDEBUG all the time.

christos